You waste money, possibly lose a job, and noting that its illegal in most states.
you ruin your life
Medical marijuana is legal in many states and is legal recreational in some. The DEA has already admitted marijuana is safer than heroin (considering they're in the same drug schedule when they shouldn't).
In California, many jobs don't care if you smoke weed. They don't check. I'm sure the same is for many medicinally legal states.
Ad who's to say its a waste of money? That seems pretty loving subjective.
Not specifically weed but having a dependency on anything is not ideal and in some cases can cause issues in your life. Having weed passively is not really an issue, it becomes an issue when you find it hard to live without it.
If you get "addicted" to weed, you probably have dependency issues with many things, not just drugs.